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Key Doesn't Turn Engine Off

S

stev

Member
Joined
Jan 8, 2022
Location
Orange, CA
I relocated my battery to my trunk and have replaced the original battery cable with new thicker cable. But ever since I haven't been able to turn off the engine by pulling the key out of the ignition. I have to pull the fuel pump fuse to get it to shut off. The car is a 1980 240 and is on ms2. And I have been dealing with a weak battery on start, my suspicion is the ecu is powered on at all times. But I haven't changed any of the original wiring the previous owner did. It seems when I pull the key out of the ignition when the car is on the power windows, radio, fans all turn off like they should but not the engine or anything related to it like the aftermarket gauges, radiator fan, or fuel pump. So I think its an ignition relay problem but I didn't change any of it. I don't know how MS or anything engine related is supposed to be wired so that's why I am asking.
 
Do you have any notes from the PO on how they wired up MS, specifically the added main&fuel relays? Did you do any other rewiring with the battery relocation? How is the +12volt junction box (black box on fender by coil) getting power now? (It usually has a short red wire off the + battery post clamp.)

As something simple, try tapping on the 2 MS relays when it won't turn off and see if one of them is stuck.

Edit: one other thought - do you have a fan relay controlled by MS? If so, try pulling the fan relay next time it won't shut off and see what happens.
 
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a long battery cable is a hazard. needs a solenoid at battery to disengage the cable when not starting. a smaller cable, properly fused, should return to the battery for recharging it.

you didn't use a thick ground cable back to the engine bay, right?


start looking at a bypassed exciter circuit at alternator, and also the brown wire at the starter, used to energize the ignition at full 12v during cranking, check where it goes.
 
Yeah I just ran one wire from the starter to the battery with a circuit breaker next to the battery. The PO didn't leave any wiring information for me but I've looked at some of the wiring under the dash, where the ecu is there are two relays, I wasn't sure if they were related to the ecu but I hear them click when I turn the ignition. Are those two if they are the main and fuel pump relay, supposed to be wired directly to the battery cable? The PO probably removed that junction box or moved it elsewhere because there wasn't anything coming off the positive terminal.
 
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Here's the commonly used MS wiring diagram for power, MS relays, and MS fuses:


The ignition key turns on the Main relay directly. MS then turns on the Fuel relay briefly to prime, and fully on once cranking/running is detected. If it stays running with key off, assuming the ignition switch is really turning off, and assuming that it's wired like the above diagram, then something else wired to switched +12v is back-driving the switched +12 enough to keep the main relay on when the key is removed.

Pictures might help, or you can start pulling relays (other than the MS main&fuel relays) and pulling non-MS fuses to help isolate the problem. If you have one, I'd start with the efan since that isn't well standardized in the MS documents.
 
Okay so I don?t want to start messing around with the ms wiring yet until ive covered some of the more obvious stuff. whenever i pull fuse 12 the car will fully die. there is still power going to that fuse after i pull the key out of the ignition. the ignition wire (yellow/blue wire) powering that fuse is not disconnecting power. and i?m assuming that yellow/blue striped wire is coming straight off the ignition. so i?ll check to see if i unplug that wire if it will kill the car. then maybe my ignition is faulty.
 
Update: I started the car, pulled the key out, then unplugged the yellow/blue wire from the fuse panel. the car still ran, so yes the ignition is really turning off, so it has to be back driven off of something else. i?ll check the relays to see how it?s wired.
 
^^^ that's great info!

I'm assuming you have the 1980 greenbook (if not, ozvolvo.org/archive). Stopping when you pull fuse 12 is a good clue. Fuse 12 is listed as: backup lights, electric windows, seat heater, A/C, plus whatever else has been added, if anything.

When it's running with key out, try shifting into reverse (brakes on) to turn on the backup lights. If it stops, you're looking for something that's weakly backdriving switched +12v.

Can you trace the main power to the MS relays back to the battery or fuse panel? I'm wondering if the MS has been added to fuse 12.
 
here are some pics of the wiring situation, you can see the main battery cables joined to a junction post with some other power cables coming off of it as well. What I don't understand is this is exactly how it was wired before but with the addition of the main battery cable running to the back of the car. So out of the three smaller cables coming off the post, there is one that goes to the ignition, and the other two go to the relays. Both relays are powered directly off of the battery 12v cable. They click on/off when i insert the key and turn it so they should be the main and fuel relays.
<a href="https://ibb.co/v33dKSf"><img src="https://i.ibb.co/8rrxSHG/IMG-1557.jpg" alt="IMG-1557" border="0" /></a>
 
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How is that big junction even insulated? It looks like it's only an inch or two away from shorting out against the brackets behind it.
 
I mean yeah that's how I bought the car, the post screws to the bracket and just has that rubber cap on it, before it was just electrical taped.
 
YIKES!!! That's some exceptional Kustom work.... My condolences. If it were me, I'd redo the whole MS install and battery relocation, but I'm pretty AR.

- What's the silver box with the black gaffers tape over it to the left of the power stage?
- Is that the main engine harness coming up through what used to be the A/C drain hole in the tunnel?
- Is the MS hidden inside the original LH ECU box?
- Do you by any chance have really crappy radio reception?
- How about some pictures of the engine compartment, including the corner where the battery and junction box are normally?
 
I would do a new wiring harness but the car would be off the road for a long time, one day hopefully I'll strip the car entirely and do a proper restoration/rebuild. I have no idea what that box is with the tape on it, but I put tape on it because the cover fell off but there was a small circuit board inside it. I believe the wires coming from the A/C hole is part of the harness, some other cables come from a hole on the driver side. I never took anything apart but the MS is probably in there, there is a cable coming from the back of the box that connects to a port on a laptop and a vacuum line that also runs in there. And I have no speakers in my car:lol:.

So there wasn't anything there previously when the battery was upfront.
<a href="https://ibb.co/6v4RBr4"><img src="https://i.ibb.co/vsJxYVJ/IMG-1560.jpg" alt="IMG-1560" border="0" /></a>
 
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There's hardly any wiring left in that corner of the engine bay! Where'd the rest of it go? (headlight relay, washer pumps, turn signals, etc.)

I'm guessing that you have the original 1980 alternator and the silver box with the black gaffers tape on it is the external voltage regulator.

On more test (in addition to shifting to reverse when running key out) - after removing fuse 12, can you restart it normally? How about a picture of the fuse panel?
 
In the diagram provided by bobxyz, the main EFI and fuel pump relay are powered up via a switched circuit from the ignition switch. Of course, given the rats nest that you have it is a guess as to whether that is how the car is wired up. If the same circuit that switches the relays is used to supply the field flashing circuit for the alternator, the alternator can back feed the circuit and keep the relays energized (and the engine running). Because this circuit runs through the dash charge light it is a high resistance (weak) path; but, once the relay coils have been energized it takes very little current to hold the relay in the closed position.

When I did my initial install of MS2 on my 142 I had this run-on problem. I initially fixed it by putting a blocking diode in the alternator flashing / exciter circuit. I later added relays to completely separate some of the circuits in the car.

It only takes a couple of minutes to carry out a test to confirm whether the exciter / flashing circuit is the problem. Isolate the voltage regulator wiring so that the alternator is disabled (no need to disconnect the B+ cable with a separate regulator). Start the car and then turn it off. If it shuts down you know you have an exciter / flashing circuit problem. If it does not shut down, then time to look for some other problem some place else.
 
^^^ That's a good idea. :nod:

The OP's problem showed up after relocating/replacing the battery&cables, which might have cleaned up some crusty connections just enough to keep the relays on when being backpowered from the the alternator bulb.

For the OP, there are a couple easy ways to check this:
1) unplug the external voltage regulator from the alternator (either at the alternator or at the silver box to the left of the powerstage), or
2) remove the alternator failure bulb from the instrument cluster.

[Note: the standard MS wiring has the coil on both main&fuel pump relays connected to switched +12v, but the PO may have connected the fuel pump relay differently. If so, the alternator bulb would only need to backpower the main relay's coil, and just enough to keep it from springing open.]
 
I don?t think my exciter wire/external voltage regulator can be blamed. I don?t have the gauge cluster installed right now or before i did the battery relocation. And I have a 100 amp Nippo Denso alternator which i think has the internal voltage regulator. And even then that exciter wire i have connected to a fuse on a different part of the fuse panel.
 
OK, no console, so the alternator light isn't the culprit. :-(

You're running a Denso, so no external voltage regulator. I looked at the first set of pics in high res, and the orange and yellow wires off the mystery silver box sure look like they say "Alternator [something]" on them. Please trace all 3 or 4 wires off that silver box and see if they go no where. If it were me, I'd remove the box, trace the wires, and remove them too.

There's lots of non-factory wiring on your fuse panel. I'll give you some comments, but this may be an issue that's not readily solvable over the internet. For factory reference, I'm looking at the TP-30057 greenbook.

First, please trace the red wires on the aftermarket blade fuse holder to the right of the main fuse panel.

Here's what I think you have wired to the main fuses (the spade on the bottom goes to the left side of the fuse, the upper 1 or 2 spades are after the fuse):

fuse 1,2 - looks factory
fuse 3 - no connect, so no heater blower
fuse 4 - switched +12v to add on solid [?] white wire to ??? - please trace this
fuse 5 - tank pump, source has been replaced with yel/red wire
fuse 6 - no connect, so no brake lights ????
fuse 7 - no connect, so main fuel pump isn't fused here
fuse 8 - looks mostly factory
fuse 9 - no connect, but expected grn/wt wire for hazard lights looks like it's miswired to fuse 10
fuse 10 - window lifts, but connected to grn/wt hazard lights ???
fuse 11 - switched +12 to add on black wire to ??? - please trace this
fuse 12 - original wire has been replaced with blue/red wire - please trace this
fuse 13 - looks factory
fuse 14 - unused
fuse 15 - looks factory
fuse 16 - from parking lights switch, weird non-factory wiring
 
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